Biodegradable composition comprising polymers of natural origin and aliphatic-aromatic copolyesters

ABSTRACT

The present invention relates to a biodegradable composition comprising at least one polymer of natural origin and at least one aliphatic-aromatic copolyester obtained starting from mixtures comprising aliphatic diols, polyfunctional aromatic acids, and at least two aliphatic dicarboxylic acids, at least one of which is long chain. Said composition combines improved biodegradability, excellent mechanical properties, a high level of industrial processability, limited environmental impact as well as stability of physical properties under the influence of environmental factors.

The present invention relates to a biodegradable composition comprisingat least one polymer of natural origin and at least onealiphatic-aromatic copolyester obtained starting from mixturescomprising aliphatic diols, polyfunctional aromatic acids, and at leasttwo aliphatic dicarboxylic acids, at least one of which is long chain.

Biodegradable aliphatic-aromatic polyesters obtained starting fromaliphatic diacids such as adipic acid, aromatic diacids such asterephthalic acid and aliphatic diols are known in the literature and tothe market. The presence of the aromatic component in the chain isrelevant to obtain polymers with sufficiently high melting temperaturesand adequate crystallization rates.

However, currently marketed polyesters of this kind have quantities ofaromatic acid of less than 48% by moles, since above this threshold thepercentage of biodegradation of these polyesters decreasessignificantly.

This markedly limits the possibility of using said polyesters forapplications where high mechanical properties associated tocompostability are needed, such as for example for the production ofbags for collecting organic waste.

Composting is the industrial process that imitates the processes,reproducing them in a controlled and accelerated form, which in naturereturn the organic substances to the life cycle. In nature the organicsubstance produced and no longer “useful” for life (dry leaves,branches, animal remains etc.) is decomposed by the micro organismspresent in the soil which brings it back to the natural cycle. The lessdegradable components remaining constitute the humus which thereforerepresents an important food supply for plants given its capacity torelease the nutritive elements (nitrogen, phosphorous, potassium etc.)slowly but constantly, ensuring constant fertility of the ground.Industrial composting is therefore a process in which structures areprovided for rational management of the microbiological activities thatoccur spontaneously in nature with the aim of reducing the timenecessary to obtain a type of humus, i.e. the compost, and improve thequality of the end product with respect to the product obtainednaturally.

In fact, it is known in the literature (Muller et al., Angew. Chem.,Int. Ed. (1999), 38, 1438-1441) that copolymers of the polybutyleneadipate-co-terephthalate type with a molar fraction of terephthalate of42% biodegrade completely in composting in 12 weeks, while products witha 51% molar fraction of terephthalate have percentages of biodegradationbelow 40%. This difference was attributed to the formation of a highernumber of butylene terephthalate sequences with a length greater than orequal to 3, which are less easily biodegradable.

If it were possible to maintain suitable biodegradation properties, anincrease in the percentage of aromatic acid in the chain wouldnonetheless be desirable, as it would allow an increase in the meltingpoint of the polyester, an increase in, or at least maintenance of,important mechanical properties, such as ultimate strength and elasticmodulus, and would also consent an increase in the crystallization rateof the polyester, thereby improving its industrial processability.

Biodegradable compositions of natural polymers with aliphatic-aromaticpolyesters are also known in the market. Because of their mechanical andbiodegradability properties, said compositions are particularly suitableto be used for producing films for food packaging and bags, particularlyfor collecting organic waste.

Still, it is known that these compositions undergo to a deterioration inphysical properties and particularly of mechanical and rheologicalproperties under the influence of one or more environmental factors,such as heat, light or chemicals.

The problem underlying the present invention is therefore that offinding a biodegradable composition comprising at least one polymer ofnatural origin and at least one aliphatic-aromatic polyester of thediacid-diol type with a high percentage of aromatic acid in the chainand capable of overcoming the drawbacks above mentioned.

Starting from this problem, it has now surprisingly been found that, bymixing specific quantities of at least one polymer of natural originwith at least one aliphatic-aromatic polyester having a molar fractionof the aromatic acid component above 48% and provided with a specificcomposition ratio of at least two aliphatic dicarboxylic acids, one ofwhich is long chain, it is possible to obtain a composition whichcombines excellent mechanical properties, a high level of industrialprocessability, limited environmental impact as well as stability ofphysical properties under the influence of environmental factors withoutcompromising, but rather improving, its biodegradation properties.

The present invention relates to a composition comprising:

(A) at least one biodegradable aliphatic-aromatic copolyester obtainablestarting from mixtures comprising at least one diol, at least onepolyfunctional aromatic acid and at least two aliphatic dicarboxylicacids, characterized in that the content of said aromatic acids iscomprised between 48 and 70% by moles with respect to the total molarcontent of dicarboxylic acids and the aliphatic dicarboxylic acidscomprise:

-   -   i from 51 to 95% by moles of at least one diacid C₄-C₆;    -   ii from 5 to 49% by moles, preferably from 30 to 49% of at least        one long chain diacid having more than 6 carbon atoms in the        main chain        (B) at least one polymer of natural origin;        wherein the concentration of (A), with respect to (A+B) is >40%,        preferably >50% and more preferably >60% in weight, said        composition having a Melt Flow Index (MFI) of 1.5-10 g/10 min,        preferably of 2-7 g/10 min.

With regards to the MFI, it is measured at 160° C. and 5 kg according tothe standard ASTM 1238-89 “Standard Test Method for Melt Flow Rates ofThermoplastics by Extrusion Plastometer”.

Advantageously, the mixture according to the present invention shows ahigh stability of physical properties, particularly in relation to theirMelt Flow Index (MFI).

In the meaning of the present invention “high stability” of MFI meansthat, after 6 months in normal storing conditions (i.e. 23° C. 55% RH),the MFI of the mixture is lower than 12 g/10 min, preferably lower than10 g/10 min, more preferably lower than 7 g/10 min.

Long chain diacids in the present invention are intended as dicarboxylicacids with more than 6 carbon atoms in the main chain. Said long chaindiacid are preferably selected from the group consisting of aliphaticdicarboxylic acids with number of C atoms in the main chain comprisedbetween 7 and 22, esters and mixtures thereof, suberic acid, azelaicacid, sebacic acid, dodecanedioic acid, brassylic acid, octadecandioicacid, their esters and mixtures thereof being particularly preferred.

In the meaning of the present invention, products obtained from sourceswhich, due to their intrinsic characteristic, are naturally regeneratedor are not exhaustible in the time scale of human life and, byextension, whose use does not compromise natural resources for futuregenerations, are considered as being of renewable origin. The use ofproducts of renewable origin also contributes to decreasing CO₂ in theatmosphere and decreasing the use of non-renewable resources. A typicalexample of renewable sources is constituted by vegetable crops.

In the copolyester (A), polyfunctional aromatic acids are intended asdicarboxylic aromatic compounds of the phthalic acid type anddicarboxylic heterocyclic aromatic compounds of renewable origin,mixtures and esters thereof. Particularly preferred are terephthalicacid and its esters and 2,5-furandicarboxylic acid and its esters, andmixtures thereof.

The content of polyfunctional aromatic acids in the copolyester (A) iscomprised between 48 and 70%, preferably between 49 and 60%, morepreferably between 49 and 58% and still more preferably between 49 and53% by moles with respect to the total molar content of dicarboxylicacids.

Examples of diols in the copolyester according to the invention are1,2-ethanediol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol,1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol,1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol,1,13-tridecanediol, 1,4-cyclohexanedimethanol, propylene glycol,neo-pentylglycol, 2-methyl-1,3-propanediol, dianhydro-sorbitol,dianhydro-mannitol, dianhydro-iditol, cyclohexanediol,cyclohexanemethanediol, and mixtures thereof. Among the diols,1,2-ethanediol, 1,4-butanediol and mixtures thereof are particularlypreferred. Advantageously, said diols are constituted by at least 50%,preferably at least 80% in moles by 1,4 butandiol with respect to thetotal diol content.

The copolyester (A) can contain, in addition to the basic monomers, atleast one hydroxy acid in a quantity comprised between 0-49%, preferablybetween 0-30% by moles with respect to the moles of the aliphaticdicarboxylic acid. Examples of suitable hydroxy acids are glycolic acid,hydroxybutyric acid, hydroxycaproic acid, hydroxyvaleric acid,7-hydroxyheptanoic acid, 8-hydroxycaproic acid, 9-hydroxynonanoic acid,lactic acid or lactic acid. The hydroxy acids can be inserted in thechain as is or can also be made to react firstly with diacids or diols.Said hydroxyacids can be present with either a random or a blockrepeating units distribution.

Long bifunctional molecules also with function not in the terminalposition can also be added in quantities not exceeding 10%. Examples aredimer acids, ricinoleic acid, and acids with epoxide functions.

Amines, amino acids and amino alcohols can also be present inpercentages up to 30% by moles with respect to all the other components.

In the preparation process of the copolyester (A), one or morepolyfunctional molecules can advantageously be added, in quantitiescomprised between 0.01 and 3% by moles with respect to the quantity ofdicarboxylic acids (and any hydroxy acids), in order to obtain branchedproducts. Examples of these molecules are glycerol, pentathritol,trimethylolpropane, citric acid, dipentaerythritol, monoanhydrosorbitol,monohydro-mannitol, acid triglycerides, undecylenic acid,triethanolamine, 1,1,2-etantricarboxylic acid;1,1,2,2-etantetracarboxylic acid, 1,3,5 pentatricarboxylic acid,1,2,3,4-cyclopentatetracarboxylic acid, malic aci, tartaric acid,3-hydroxyglutaric acid, mucic acid, trihydroxyglutaric acid,hydroxy-isophthalic acid, esantriol, sorbitol, trimethiletane, mannitol,1,2,4 butantriol, xilitol, 1,2,4,4-tetrakis(hydroxymethyl)cyclohexane,arabitol, adonitol, iditol.

The molecular weight M_(n) of the copolyester (A) is greater than15,000, preferably greater than 30,000, more preferably greater than40,000. The polydispersity index M_(w)/M_(n) is comprised between 1.5and 10, preferably between 1.6 and 5 and more preferably between 1.7 and3. The molecular weights Mn and Mw can be measured using Gel PermeationChromatography (GPC). Determination can be conducted with thechromatography system maintained at 40° C., using a set of three columnsin series (particle diameter of 5μ and porosity respectively of 500 Å,1000 Å and 10000 Å), a refraction index detector, chloroform as eluent(flow rate 1 ml/min) and using polystyrene as standard of reference.

The copolyester (A) has an inherent viscosity (measured with Ubbelhodeviscometer for solutions in CHCl₃ with concentration 0.2 g/dl at 25° C.)greater than 0.5 dl/g, preferably greater than 0.6 dl/g and even morepreferably greater than 0.7 dl/g.

The production process of the copolyester (A) can take place accordingto any one of the processes known to the state of the art. Inparticular, the copolyester can advantageously be obtained with apolycondensation reaction.

Advantageously, the polymerization process of the copolyester (A) can beconducted in the presence of a suitable catalyst. By way of example,suitable catalysts can be organometallic compounds of tin, i.e.derivatives of stannoic acid, titanium compounds, such as ortho-butyltitanate, aluminum compounds such as Al-triisopropyl, antinomy compoundsand zinc compounds.

Preferably, the copolyester (A) is obtainable by reacting at least oneprecursor polyester PP having at least one acid component and at leastone diol component with compounds carrying groups which can react withOH and/or COOH groups, such as for example, polyepoxides andpolycarbodiimides or with radical initiators.

Said compounds can be used also in mixture.

Said at least one precursor polyester PP may be of the aliphatic,aromatic or aliphatic-aromatic type.

The skilled person will easily be able to identify the actual molarratios necessary with respect to the nature of the precursor polyestersPP so as to obtain the desired copolyester (A). Preferably, thecopolyester (A) is obtainable by a reactive extrusion process.

Among radical initiators, preferred are peroxides and among peroxidesparticularly preferred are organic peroxides. Organic peroxides canadvantageously selected from the group consisting of: benzoyl peroxide,lauroyl peroxide, isononanoyl peroxide,di-(t-butylperoxyisopropyl)benzene, t-butyl peroxide, dicumyl peroxide,alpha,alpha′-di(t-butylperoxy)diisopropylbenzene, 2,5-dimethyl-2,5di(t-butylperoxy)hexane, t-butyl cumyl peroxide, di-t-butylperoxide,2,5-dimethyl-2,5-di(t-butylperoxy)hex-3-yne,di(4-t-butylcyclohexyl)peroxydicarbonate, dicetyl peroxydicarbonate,dimyristyl peroxydicarbonate,3,6,9-triethyl-3,6,9-trimethyl-1,4,7-triperoxonan,di(2-ethylhexyl)peroxydicarbonate and mixtures thereof.

Preferably, said peroxides are added to the at least one precursorpolyester PP in a quantity of less than 0.1%, more preferably of 0.05%and even more preferably of 0.02% by weight. Examples of polyepoxidesthat can advantageously be used are all polyepoxides from epoxidizedoils and/or from styrene-glycidyl ether-methylmetacrylate, such asproducts distributed by BASF Resins B.V. under the trademark Joncryl®ADR, glycidyl ether methylmetacrylate included in a range of molecularweights between 1000 and 10000 and with a number of epoxides permolecule ranging from 1 to 30 and preferably from 5 to 25, and epoxidesselected from the group comprising: diethylene glycol diglycidyl ether,polyethylene glycol diglycidyl ether, glycerol polyglycidyl ether,diglycerol polyglycidyl ether, 1,2-epoxybutane, polyglycerolpolyglycidyl ether, isoprene diepoxide, and cycloaliphatic diepoxide,1,4-cyclohexanedimethanol diglycidyl ether, glycidyl 2-methylphenylether, glycerol propoxylate triglycidyl ether, 1,4-butanediol diglycidylether, sorbitol polyglycidyl ether, glycerol diglycidyl ether,tetraglycidyl ether of meta-xylenediamine and diglycidyl ether ofbisphenol A, and mixtures thereof.

Preferably, said polyepoxides are added to the at least one precursorpolyester PP in a quantity of less than 2%, more preferably of 1% andeven more preferably of 0.75% by weight.

Catalysts can also be used to increase the reactivity of the reactivegroups. In the case of polyepoxides, salts of fatty acids can, forexample, be used. Calcium and zinc stearates are particularly preferred.

Examples of carbodiimides that can advantageously be used are selectedfrom the group comprising: poly(cyclooctylene carbodiimide),poly(1,4-dimethylene cyclohexylene carbodiimide), poly(cyclohexylenecarbodiimide, poly(ethylene carbodiimide), poly(butylene carbodiimide),poly(isobutylene carbodiimide), poly(nonylene carbodiimide),poly(dodecylene carbodiimide), poly(neopentylene carbodiimide),poly(1,4-dimethylene phenylene carbodiimide), poly(2,2′,6,6′,tetra-isopropyl-diphenylene carbodiimide), (Stabaxol® D),poly(2,4,6-triisopropyl-1,3-phenylene carbodiimide) (Stabaxol® P-100),poly(1,3,5-triisopropyl-phenylene-2,4-carbodiimide), poly(2,6diisopropyl-1,3-phenylene carbodiimide) (Stabaxol® P), poly(tolylcarbodiimide), poly(4,4′-diphenylmethane carbodiimide),poly(3,3′-dimethyl-4,4′-biphenylene carbodiimide), poly(p-phenylenecarbodiimide), poly(m-phenylene carbodiimide),poly(3,3′-dimethyl-4,4′-diphenylmethane carbodiimide), poly(naphthylenecarbodiimide), poly(isophorone carbodiimide), poly(cumene carbodiimide),p-phenylene bis(ethylcarbodiimide), 1,6-hexamethylenebis(ethylcarbodiimide), 1,8-octamethylene bis(ethylcarbodiimide),1,10-decamethylene bis(ethylcarbodiimide), 1,12 dodecamethylenebis(ethylcarbodiimide) and mixtures thereof. Preferably, saidcarbodiimides are added to the at least one precursor polyester PP in aquantity of less than 1.5%, more preferably of 0.75% and even morepreferably of 0.5% by weight.

Said at least one precursor polyester PP may preferably have anunsaturation content of 0.1-0.8 and more preferably of 0.2-0.7% inmoles.

Said unsaturations can be generated in situ during the polymerizationphase or during processing of the at least one precursor polyester,through the addition of suitable unsaturated monomers or suitableunsaturated chain terminators,

Particularly preferred are precursor polyesters PP with terminalunsaturations.

Among unsaturated chain terminators, preferred are those having formula:

T-(CH₂)_(n)—CH═CH₂

wherein “T” is a group able to react with carboxylic and/or hydroxylicgroups and “n” is an integer number comprised between 0 and 13.

Said unsaturated chain terminators can also be used in mixture.

With regard to “T”, it is preferably selected from the group consistingof hydroxylic, carboxylic, amine, amide or ester group, hydroxylic orcarboxylic groups being particularly preferred.

The integer “n” is preferably comprised between 1 and 13, morepreferably 3 and 13, still more preferably 8 or 9, omega-undecenoicacid, omega-undecylenic alcohol and mixtures thereof being particularlypreferred in order to maximize compatibility with the at least onepolymer of natural origin.

Also after the preparation process, the copolyester (A) can have doublebonds and/or adducts deriving from the reaction of the unsaturationswith the radical initiators.

The presence of the unsaturations and/or adducts deriving from theirreaction with the radical initiators can be determined with differentmethods well known to those skilled in the art, such as NMR spectroscopyor by methanolysis reactions of the polymer chain coupled withchromatographic methods combined with mass spectrometry.

The skilled person will easily be able to identify structures referableeither to the unsaturations or to the reacted unsaturation after thereaction.

Preferably, the polyester (A) is obtainable through a reactive extrusionprocess starting from a precursor polyester PP having a content ofterminal acid groups in quantities of 35-150 meq of KOH/kg of theprecursor polyester.

The measurement of terminal acid groups can be carried out as follows:1, 5-3 g of the polyester according to the invention are placed into a100 ml Erlenmeyer flask. 60 ml of chloroform are added to dissolve theresin. After complete dissolution 25 ml of 2-propanol and, just beforethe determination, 1 ml of deionised water are added. The solution thusobtained is titrated with a preliminary standardized KOH/ethanolsolution using a suitable indicator for the determination of theequivalence point of the titration, such as for example a glasselectrode designed for use with nonaqueous acid-base titrations. Theterminal acid group content is calculated from the consumption of theKOH/ethanol solution based on the following equation:

${{Terminal}\mspace{14mu} {acid}\mspace{14mu} {group}\mspace{14mu} {content}\mspace{14mu} \left( {{meq}\mspace{14mu} {KOH}\text{/}{kg}\mspace{14mu} {of}\mspace{14mu} {polymer}} \right)} = \frac{\left\lfloor {\left( {V_{eq} - V_{b}} \right) \cdot T} \right\rfloor \cdot 1000}{P}$

wherein:

-   -   V_(eq)=ml of KOH/ethanol solution at the equivalence point for        the titration of the sample;    -   V_(b)=ml of KOH/ethanol solution necessary to arrive at pH=9.5        during the blank titration;    -   T=concentration in moles/1 of the KOH/ethanol solution;    -   P=g of sample.

The copolyester (A) is biodegradable in industrial composting inaccordance with the standard EN 13432.

The at least one polymer of natural origin (B) is advantageouslyselected from starch, cellulose, chitin, chitosan, alginates, proteinssuch as gluten, zein, casein, collagen, gelatin, natural rubbers, rosinacid and its derivatives, lignins and their derivatives. Starches andcelluloses can be modified and among these it is possible mentioning,for example, starch or cellulose esters with degree of substitutioncomprised between 0.2 and 2.5, hydroxypropylated starches, modifiedstarches with fatty chains.

Among the polymers of natural origin above mentioned, starch isparticularly preferred.

The term starch is intended herein as all types of starch, for examplepotato starch, corn starch, tapioca starch, pea starch, rice starch,wheat starch and also high-amylose starch—preferably containing morethan 30% by weight of amylose—and waxy starches. Particularly preferredare also mixtures of starches.

The starch can be used in destructurized or gelatinized form or infiller form. Said starch can represent the continuous or dispersed phaseor can be in co-continuous form.

In general, to obtain co-continuous structures it is possible to workeither on the selection of starch with high amylopectine content and/orto add to the starch-polyester compositions block copolymers withhydrophobic and hydrophilic units. Possible examples arepolyvinylacetate/polyvinylalcohol and polyester/polyether copolymers inwhich the block length, the balance between the hydrophilicity andhydrophobicity of the blocks and the quality of compatibilizer used canbe suitably changed in order to finely adjust the microstructure of thestarch-polyester compositions.

In the case of dispersed starch, the starch represent preferably anhomogeneously dispersed phase of particles with mean dimensions of lessthan 1 μm, preferably less than 0.8 μm.

The dimensions of starch particles are measured in the transversesection with respect to the direction of the extrusion flow or, anyhow,with respect to the direction of material's output. For this purpose asample of the mixture which is to be examined is immersed in liquidnitrogen and subsequently fractured so as to obtain a fracture surfacealong a cross-section of the sample. The portion of the sample which isto be examined is then subjected to selective etching, dried and a thinlayer of metal is deposited thereupon, for example a mixture ofgold/palladium, using a “sputter coater”. Finally the surface of thefracture is examined under a scanning electron microscope (SEM).

The dimension of starch particles is determined measuring the dimensionsof the holes on the surface of the fracture after the selective etchingof starch.

The mean dimension of the starch particles, i.e. the holes detectable onthe etched surface of the fracture, is calculated as the numeral (orarithmetic) average of the particles dimensions. In case of a sphericalparticle the dimension of the particle corresponds to the diameter of acircle corresponding to the bidimensional shape resulting from thetransverse section. In case of a non-spherical particle the dimension(d) of the particle is calculated according to the following formula:

d=√{square root over (d ₁ ·d ₂)}

where d₁ is the minor diameter and d₂ is the major diameter of theellipse in which the particle can be inscribed or approximated.

The selective etching of starch dispersed phase, may be advantageouslyperformed with HCl 5 N as etchant with an etching time of 20 minutes atan etching temperature of 25° C. Mixtures containing destructurizedstarch are preferred.

Starches such as corn and potato starch, capable of being easilydestructurizable and which have high initial molecular weights, haveproven to be particularly advantageous.

The use of corn and potato starch is particularly preferred.

For destructurized starch, the teachings contained in EP-O 118 240 andEP-O 327 505 are referred to here, this being intended as starchprocessed so that it substantially has no “Maltese crosses” under theoptical microscope in polarized light and no “ghosts” under the opticalmicroscope in phase contrast.

Furthermore, physically and chemically modified starch grades can beused, such as ethoxylated starches, oxypropylated starches, starchacetates, starch butyrate, starch propionates, with a substitutiondegree comprised within the range of from 0.1 to 2, cationic starches,oxidized starches, crosslinked starches, gelled starches.

Mixtures according to the present invention wherein starch represent thedispersed phase can form biodegradable polymeric compositions with goodresistance to ageing and to humidity. Indeed, these polymericcompositions can maintain a high tear strength even in condition of lowhumidity.

Such characteristics can be achieved when the water content of thecomposition during mixing of the component is preferably kept between 1%and 15% by weight. It is, however, also possible to operate with acontent of less than 1% by weight, in this case, starting with predriedand pre-plasticized starch.

It could be useful also to degrade starch at a low molecular weightbefore or during compounding with the polyesters of the presentinvention in order to have in the final material or finished product astarch inherent viscosity between 1 and 0.2 dl/g, preferably between 0.6and 0.25 dl/g, more preferably between 0.55 and 0.3 dl/g.

Destructurized starch can be obtained before or during the mixing withthe polyesters according to the present invention in presence ofplasticizers such as water, glycerol, di and poly glycerols, ethylene orpropylene glycol, ethylene and propylene diglycol, polyethylene glycol,polypropylenglycol, 1,2 propandiol, trymethylol ethane, trymethylolpropane, pentaerytritol, dipentaerytritol, sorbitol, erytritol, xylitol,mannitol, sucrose, 1,3 propanediol, 1,2 butanediol, 1,3 butanediol, 1,4butanediol, 1,5 pentanediol, 1,5 hexanediol, 1,6 hexanediol, 1,2,6hexanetriol, 1,3,5 hexanetriol, neopentyl glycol and polyvinyl alcoholprepolymers and polymers, polyols acetates, ehtoxylates andpropoxylates, particularly sorbitol ethoxylate, sorbitol acetate, andpentaerythritol acetate.

Water can be used as a plasticizer in combination with high boilingpoint plasticizers or alone during the plastification phase of starchbefore or during the mixing of the composition and can be removed at theneeded level by degassing on one or more steps during extrusion. Uponcompletion of the plastification and mixing of the components, the wateris removed by degassing to give a final content of about 0, 2-3% byweight.

Water, as well as high-boiling point plasticizers, modifies theviscosity of the starch phase and affects the rheological properties ofthe starch/polymer system, helping to determine the dimensions of thedispersed particles. Compatibilizers can be also added to the mixture.They can belong to the following classes:

-   -   Additives such as esters which have hydrophilic/lipophilic        balance index values (HLB) greater than 8 and which are obtained        from polyols and from mono or polycarboxylic acids with        dissociation constants pK lower than 4.5 (the value relates to        pK of the first carboxyl group in the case of polycarboxylic        acids)    -   Esters with HLB values of between 5.5 and 8, obtained from        polyols and from mono or polycarboxylic acids with less than 12        carbon atoms and with pK values greater than 4.5 (this value        relates to the pK of the first carboxylic group in the case of        polycarboxylic acids)    -   Esters with HLB values lower than 5.5 obtained from polyols and        from fatty acids with 12-22 carbon atoms.

These compatibilizers can be used in quantities of from 0.2 to 40%weight and preferably from 1 to 20% by weight related to the starch. Thestarch blends can also contain polymeric compatibilizing agents havingtwo components: one compatible or soluble with starch and a second onesoluble or compatible with the polyester.

Examples are starch/polyester copolymers through transesterificationcatalysts. Such polymers can be generated trough reactive blendingduring compounding or can be produced in a separate process and thenadded during extrusion. In general block copolymers of an hydrophilicand an hydrophobic units are particularly suitable. Additives such as diand polyepoxides, di and poly isocyanates, isocyanurates,polycarbodiimides and peroxides can also be added. They can work asstabilizers as well as chain extenders.

All the products above can help to create the needed microstructure.

It is also possible to promote in situ reactions to create bonds betweenstarch and the polymeric matrix. Also aliphatic-aromatic polymers chainextended with aliphatic or aromatic diisocyanates or di and polyepoxidesor isocyanurates or with oxazolines with intrinsic viscosities higherthan 1 dl/g or in any case aliphatic-aromatic polyesters with a ratiobetween Mn and MFI at 190° C., 2.16 kg higher than 10 000, preferablyhigher than 12 500 and more preferably higher than 15 000 can also beused to achieve the needed microstructure.

Another method to improve the microstructure is to achieve starchcomplexation in the starch-polyester mixture.

The composition according to the present invention shows good propertiesalso in case of starch blends in which the starch is not stronglycomplexed. With regard to the complexation of the starch, the teachingscontained in EP-0 965 615 have to be intended as incorporated in thepresent description. The presence of the complexes of starch with onehydrophobic polymer incompatible with the starch can be demonstrated bythe presence in the X-ray diffraction spectra of a peak in the range ofthe 13-14° on the 2 theta scale. According to the present invention,with the wording compositions in which the starch is not stronglycomplexed are intended the compositions where the Hc/Ha ratio betweenthe height of the peak (Hc) in the range of 13-14° of the complex andthe height of the peak (Ha) of the amorphous starch which appears atabout 20.5° is less than 0.15 and even less than 0.07. Advantageously,the composition according to the present invention contains at least oneplasticizer for the starch to provide suitable rheological properties.This plasticizer can simply be water (even the water contained in thenative starch alone without the need for further additions), or highboiling or polymeric plasticizers. Mixtures of different plasticizersare also preferred.

The quantity of plasticizer is generally chosen on the basis ofrheological needs and of the mixing system. In any case, plasticizersare advantageously added in a quantity of less than 30%, preferably lessthan 20%, still more preferably less than 10% in weight in relation tothe starch on a dry basis.

Besides water, plasticizers that can be utilized in the compositionaccording to the invention are high boiling or polymeric plasticizers.

In the meaning of the present invention, high boiling plasticizers aremeant plasticizers with boiling point higher >250° C. Among these, thosedescribed in WO 92/14782, glycerol, diglycerol, triglycerol andtetraglycerol and mixtures thereof are preferred.

Particularly preferred are also mixtures of high boiling plasticizerscontaining at least 75% in weight, preferably 90% in weight ofdiglycerol, triglycerol and tetraglycerol. Said mixtures contain morethan 50% in weight, preferably more than 80% in weight of diglycerolwith respect to the total weight of diglycerol, triglycerol andtetraglycerol. The use of this type of high boiling plasticizers isparticularly preferred as they prevent problems with fumes in processingenvironments and there are no frequent shutdowns made necessary forcleaning the machines during the composition processing.

In the meaning of the present patent application, with the termdiglycerol are herein meant all compounds deriving from condensationreactions of two molecules of glycerol, such as alpha-alpha′ diglycerol,alpha-beta diglycerol, beta-beta′ diglycerol, their various cyclicisomers and mixtures thereof. As far as diglycerol is concerned,particularly preferred are mixtures comprising at least 70% in weight ofalpha-alpha′ diglycerol.

Compositions according to the present invention containing water as theonly plasticizer are also preferred. Among these, compositionscontaining the water present in native starch as the only plasticizerparticularly preferred.

The compositions according to the present invention are biodegradable inindustrial composting in accordance with the standard EN 13432.

The composition according to the invention can be used in blends, whichmay also be obtained by reactive extrusion processes, with one or morepolymers which may or may not be biodegradable.

In the meaning of this invention by biodegradable polymers are meantbiodegradable polymers according to standard EN 13432.

In particular the composition according to the invention may be blendedwith biodegradable polyesters of the diacid-diol, hydroxyacid orpolyester-ether type.

As far as the said biodegradable polyesters of the diacid-diol type areconcerned, these may be either aliphatic or aliphatic-aromatic.

The biodegradable aliphatic polyesters from diacid-diols comprisealiphatic diacids and aliphatic diols, while the biodegradablealiphatic-aromatic polyesters have an aromatic part mainly comprisingaromatic acids with multiple functional groups of, the aliphatic partbeing constituted by aliphatic diacids and aliphatic diols.

The aromatic aliphatic biodegradable polyesters from diacids-diols arepreferably characterised by an aromatic acids content of between 30 and90% in moles, preferably between 45 and 70% in moles with respect to theacid component.

Preferably the aromatic acids having multiple functional groups mayadvantageously be dicarboxylic aromatic compounds of the phthalic acidtype and their esters, preferably terephthalic acid.

The aromatic acids with multiple functional groups may also be selectedfrom the group comprising of heterocyclic dicarboxylic aromatic acids,among which 2,5-furandicarboxylic acid and its esters are preferred.

Biodegradable aliphatic-aromatic polyesters from diacids-diols in whichthe aromatic diacid component comprises a mixture of dicarboxylicaromatic compounds of the phthalic acid type and heterocyclicdicarboxylic aromatic acids are particularly preferred.

The aliphatic diacids of the biodegradable aliphatic-aromatic polyestersare aliphatic dicarboxylic acids such as oxalic acid, malonic acid,succinic acid, glucaric acid, adipic acid, pimelic acid, suberic acid,azelaic acid, sebacic acid, undecandioic acid, dodecanoic acid andbrassilic acid, their esters and their mixtures. Among these adipic acidand dicarboxylic acids from renewable sources are preferred, and amongthese dicarboxylic acids from renewable sources such as succinic acid,sebacic acid, azelaic acid, undecanedioic acid, dodecanedioic acid andbrassilic acid and their mixtures are particularly preferred.

Examples of aliphatic diols in biodegradable polyesters fromdiacids-diols are: 1,2-ethanediol, 1,2-propanediol, 1,3-propanediol,1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol,1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol,1,12-dodecanediol, 1,13-tridecanediol, 1,4-cyclohexanedimethanol,neopentylglycol, 2-methyl-1,3-propanediol, dianhydrosorbitol,dianhydromannitol, dianhydroiditol, cyclohexanediol,cyclohexanemethanediol and their mixtures. Of these, 1,4-butanediol,1,3-propanediol and 1,2-ethanediol and their mixtures are particularlypreferred.

Preferably the blends of the composition according to the invention withbiodegradable polyesters from diacids-diols described above arecharacterised by a content of the said biodegradable polyesters whichvaries within the range between 1 and 99% by weight, more preferablybetween 5 and 95% by weight with respect to the sum of the weights ofthe composition according to the invention and the former respectively.

The preferred biodegradable polyesters from hydroxy acids include:poly-L-lactic acid, poly-D-lactic acid and poly-D-L-lactic acidstereocomplex, poly-c-caprolactone, polyhydroxybutyrate,polyhydroxybutyrate valerate, polyhydroxybutyrate propanoate,polyhydroxybutyrate hexanoate, polyhydroxybutyrate decanoate,polyhydroxybutyrate dodecanoate, polyhydroxybutyrate hexadecanoate,polyhydroxybutyrate octadecanoate andpoly-3-hydroxybutyrate-4-hydroxybutyrate. Among the biodegradablepolyesters from hydroxy acids those particularly preferred arepoly-L-lactic acid, poly-D-lactic acid and stereo-complex ofpoly-L-lactic and poly-D-lactic acid.

Preferably the blends of the composition according to the invention withthe biodegradable polyesters from hydroxy acids described above arecharacterised by a content of the said biodegradable polyesters whichvaries within the range between 1 and 99% by weight, more preferablybetween 5 and 95% by weight with respect to the sum of the weights ofthe composition according to the invention and the former respectively.

The composition according to the invention may also be blended withpolyolefins, non-biodegradable polyesters, polyester- andpolyether-urethanes, polyurethanes, polyamides, polyamino acids,polyethers, polyureas, polycarbonates and mixtures thereof.

Among the polyolefins, polyethylene, polypropylene, their copolymers,polyvinyl alcohol, polyvinyl acetate, polyethylvinyl acetate andpolyethylenevinyl alcohol are preferred. Among the non-biodegradablepolyesters, PET, PBT, PTT in particular with a renewables content >30%and polyalkylene furandicarboxylates are preferred. Among the latterpolyethylene furandicarboxylate, polypropylene furandicarboxylate,polybutylene furandicarboxylate and their mixtures are preferred.

Examples of polyamides are: polyamide 6 and 6.6, polyamide 9 and 9.9,polyamide 10 and 10.10, polyamide 11 and 11.11, polyamide 12 and 12.12and their combinations of the 6/9, 6/10, 6/11 and 6/12 type.

The polycarbonates may be polyethylene carbonates, polypropylenecarbonates, polybutylene carbonates and their mixtures and copolymers.

The polyethers may be polyethylene glycols, polypropylene glycols,polybutylene glycols, their copolymers and their mixtures havingmolecular weights between 70,000 and 500,000. Preferably the blends ofthe composition according to the invention with the polymers describedabove (polyolefins, non-biodegradable polyesters, polyester- andpolyether-urethanes, polyurethanes, polyamides, polyamino acids,polyethers, polyureas, polycarbonates and mixtures thereof) arecharacterised by a content of the said polymers which varies within therange from 0.5 to 99% by weight, more preferably from 5 to 50% by weightwith respect to the sum of the weights of the composition according tothe invention and the former respectively.

The composition according to the invention can advantageously be used inblends with 5-30%, preferably 7-25% by weight of at least one rigidpolymer with a modulus greater than 1,500 MPa. Said at least rigidpolymer can be present as a further dispersed phase as well in lamellarstructures or mixtures thereof.

As far as said further dispersed phase is concerned, said at least rigidpolymer forms an homogeneously dispersed phase of particles with meandimensions of less than 2 μm, preferably less than 1 μm.

The dimensions of said particles are measured according to the method ofmeasurement above disclosed for the starch particles.

Among rigid polymers, particularly preferred are polyhydroxyalkanoates,such as polylactic acid and polyglycolic acid and more preferablypolymers or copolymers of polylactic acid containing at least 75% ofL-lactic or D-lactic acid or combinations thereof, advantageously withmolecular weight Mw greater than 70,000. Said rigid polymers can also beplasticized. The selective etching of polylactic acid dispersed phase,may be advantageously performed with acetone as etchant with an etchingtime of 5 minutes at an etching temperature of 25° C. The compositionaccording to the present invention can be prepared by means of anextruder or any other machine capable of providing temperature and shearconditions that allows an homogeneous mixing of the components.

The composition according to the present invention are advantageouslyobtainable by reactive extrusion process with compounds carrying groupswhich can react with OH and/or COOH groups, such as for example,polyepoxides and polycarbodiimides or unsaturated bonds such as forexample peroxides.

Examples of peroxides that can advantageously be used are selected fromthe group of dialkyl peroxides, such as: benzoyl peroxide, lauroylperoxide, isononanoyl peroxide, di-(t-butylperoxyisopropyl)benzene,t-butyl peroxide, dicumyl peroxide,alpha,alpha′-di(t-butylperoxy)diisopropylbenzene, 2,5-dimethyl-2,5di(t-butylperoxy)hexane, t-butyl cumyl peroxide, di-t-butylperoxide,2,5-dimethyl-2,5-di(t-butylperoxy)hex-3-yne,di(4-t-butylcyclohexyl)peroxydicarbonate, dicetyl peroxydicarbonate,dimyristyl peroxydicarbonate,3,6,9-triethyl-3,6,9-trimethyl-1,4,7-triperoxonan,di(2-ethylhexyl)peroxydicarbonate and mixtures thereof.

Preferably, said peroxides are added to the polyesters according to theinvention in a quantity of less than 0.5%, more preferably of 0.2% andeven more preferably of 0.1% by weight. Examples of polyepoxides thatcan advantageously be used are all polyepoxides from epoxidized oilsand/or from styrene-glycidyl ether-methylmetacrylate, such as productsdistributed by BASF Resins B.V. under the trademark Joncryl® ADR,glycidyl ether methylmetacrylate included in a range of molecularweights between 1000 and 10000 and with a number of epoxides permolecule ranging from 1 to 30 and preferably from 5 to 25, and epoxidesselected from the group comprising: diethylene glycol diglycidyl ether,polyethylene glycol diglycidyl ether, glycerol polyglycidyl ether,diglycerol polyglycidyl ether, 1,2-epoxybutane, polyglycerolpolyglycidyl ether, isoprene diepoxide, and cycloaliphatic diepoxide,1,4-cyclohexanedimethanol diglycidyl ether, glycidyl 2-methylphenylether, glycerol propoxylate triglycidyl ether, 1,4-butanediol diglycidylether, sorbitol polyglycidyl ether, glycerol diglycidyl ether,tetraglycidyl ether of meta-xylenediamine and diglycidyl ether ofbisphenol A, and mixtures thereof.

Preferably, said polyepoxides are added to the polyesters according tothe invention in a quantity of less than 2%, more preferably of 1% andeven more preferably of 0.75% by weight.

Catalysts can also be used to increase the reactivity of the reactivegroups. In the case of polyepoxides, salts of fatty acids can, forexample, be used. Calcium and zinc stearates are particularly preferred.

Examples of carbodiimides that can advantageously be used are selectedfrom the group comprising: poly(cyclooctylene carbodiimide),poly(1,4-dimethylene cyclohexylene carbodiimide), poly(cyclohexylenecarbodiimide, poly(ethylene carbodiimide), poly(butylene carbodiimide),poly(isobutylene carbodiimide), poly(nonylene carbodiimide),poly(dodecylene carbodiimide), poly(neopentylene carbodiimide),poly(1,4-dimethylene phenylene carbodiimide), poly(2,2′,6,6′,tetra-isopropyl-diphenylene carbodiimide), (Stabaxol® D),poly(2,4,6-triisopropyl-1,3-phenylene carbodiimide) (Stabaxol® P-100),poly(1,3,5-triisopropyl-phenylene-2,4-carbodiimide), poly(2,6diisopropyl-1,3-phenylene carbodiimide) (Stabaxol® P), poly(tolylcarbodiimide), poly(4,4′-diphenylmethane carbodiimide),poly(3,3′-dimethyl-4,4′-biphenylene carbodiimide), poly(p-phenylenecarbodiimide), poly(m-phenylene carbodiimide),poly(3,3′-dimethyl-4,4′-diphenylmethane carbodiimide), poly(naphthylenecarbodiimide), poly(isophorone carbodiimide), poly(cumene carbodiimide),p-phenylene bis(ethylcarbodiimide), 1,6-hexamethylenebis(ethylcarbodiimide), 1,8-octamethylene bis(ethylcarbodiimide),1,10-decamethylene bis(ethylcarbodiimide), 1,12 dodecamethylenebis(ethylcarbodiimide) and mixtures thereof. Preferably, saidcarbodiimides are added to the polyesters according to the invention ina quantity of less than 1.5%, more preferably of 0.75% and even morepreferably of 0.5% by weight.

In the present biodegradable composition various additives can also beincorporated, such as antioxidants, UV stabilizers, heat and hydrolysisstabilizers, chain extenders, flame retardants, slow release agents,inorganic and organic fillers, such as natural fibres, antistaticagents, wetting agents, colorants, lubricants or compatibilizing agentsamong the various phases. Preferably, the compositions according to thepresent invention show a puncture energy, measured on films havingthickness of 10-50 μm, higher than 7 J/mm more preferably more than 9J/mm and more preferably more than 12 J/mm

As regards to the measurement of puncture energy, it is performedaccording to the standard ASTM D5748-95 (2001), using a triangularpyramid shaped probe (edges=35 mm; vertex angles=90°) at a crossheadspeed of 500 mm/min, temperature of 23° C., Relative Humidity of 55% onfilm specimens having a diameter of 125 mm.

As a reference, in the same testing conditions an HDPE film withthickness of 22 μm shows a puncture energy of 9.2 J/mm whereas an LDPEfilm with thickness of 40 μm shows a puncture energy of 10 J/mm.

The composition according to the invention has properties and viscosityvalues which make it suitable to be used, appropriately modulating therelative molecular weight, for numerous practical applications, such asfilms, injection molding articles, extrusion coatings, fibers, foams,thermoformed articles, etc.

In particular, said composition and blends thereof are suitable for theproduction of:

-   -   mono- and bi-oriented films, and films multilayered with other        polymeric materials;    -   films for use in the agricultural sector, such as films for use        in mulching;    -   cling films for use with foodstuffs, for bales in agriculture,        and for wrapping waste;    -   bags and bin liners for the organic waste collection, such as        the collection of food scraps and gardening waste;    -   seed dressings;    -   glues such as hot melt adhesives;    -   thermoformed foodstuff packaging, both mono- and multi-layered,        as in containers for milk, yogurt, meats, beverages, etc;    -   coatings obtained using the extrusion coating method;    -   multilayer laminates with layers of paper, plastic, aluminum, or        metalized films;    -   expanded or expandable beads for the production of pieces        obtained by sintering;    -   expanded and semi-expanded products, including foam blocks        formed using pre-expanded particles;    -   foam sheets, thermoformed foam sheets, and containers obtained        from them for use in foodstuff packaging;    -   fruit and vegetable containers in general;    -   composites with gelatinized, destructurized and/or complexed        starch, natural starch, flours or vegetable or inorganic natural        fillers;    -   fibers, microfibers, composite microfibers wherein the core is        constituted by rigid polymers such as PLA, PET, PTT and the        shell is constituted by the biodegradable polyester according to        the invention, blended composite fibers, fibers with different        sections, from circular to multilobed, staple fibers, woven and        nonwoven fabrics or spunbonded or thermobonded for use in        sanitary and hygiene products, and in the agricultural and        clothing sectors.

They can also be used in applications in place of plasticized PVC.

The composition according to the present invention is biodegradable inaccordance with the standard EN 13432.

The invention is now described with some examples of embodiment providedpurely by way of non-limiting example of the scope of protection of thepresent patent application.

EXAMPLE 1

68 parts by weight of an aliphatic-aromatic copolyester, obtainedstarting from butanediol and the following mixture of dicarboxylic acid:

50% mol Terephthalic Acid 26% mol Adipic Acid

24% mol Sebacic acidhaving MFR of 3 g/10′.were blended with 10 parts of poly L-lactide polymer having, MFR at 190°C., 2.16 kg of 3.5 g/10 min, a residue of lactide less than 0.2% and a Dcontent of about 6%, 16.5 parts of starch, 2.5 parts of water, 3 partsof triglycerol and 0.5 parts of a styrene-glicidylether-methylmetacrylate copolymer. The extruder used was a twin screwextruder Haake Rheocord 90 Rheomex TW-100. The thermal profile wasranging between 120 and 190° C. The final water content of the granuleswas equal to 0.8% The granules were filmed on a 40 mm Ghioldi machine,die gap=1 mm, flow rate 20 kg/h to obtain film with a thickness of 20μm.

The 20 μm films were then subjected to mechanical characterizationaccording to the standard ASTM D882 (traction at 23° C. and 55%;Relative humidity and Vo=50 mm/min), to Elmendorf tear strengthmeasurement according to ASTMD1922 standard (at 23° C. and 55% H.R) andaccording to the standard ASTM D5748-95 (2001) (triangular pyramidshaped probe with edges=35 mm and vertex angles=90°; crosshead speed of500 mm/min, temperature of 23° C., Relative Humidity of 55%, filmspecimen diameter of 125 mm)

The results are indicated in Table 1 below.

TABLE 1 MECHANICAL PROPERTIES Elmendorf Puncture σ_(b) ε_(b) E Tearstrenght energy En_(b) Ex (MPa) (%) (MPa) (N/mm) (J/mm) 1 33 270 400 MD230 14 TD 151

Determination of Starch Particles Dimension

The granules of the composition according to Example 1 were immersed inliquid nitrogen and subsequently fractured so as to obtain a fracturesurface along a cross-section of samples transverse section. A portionof said samples were then subjected to etching with HCl 5 N (25° C., 20minutes), dried and a thin layer of a gold/palladium mixture wasdeposited thereupon by means of a “sputter coater”.

Finally the so obtained fracture surfaces were examined under a scanningelectron microscope (SEM) (magnification×4000). For each sample, severalmicrophotographies of the fracture surfaces were recorded. The meandimension of the starch particles was calculated as the numeral (orarithmetic) average of the particles dimension.

The composition according to Example 1 showed an average particle sizedispersed starch of 0.25 nm

Biodegradation Test

Biodegradation tests were performed according to the EN 13432 standardon films samples obtained from the composition of Examples 1.

The composition showed a relative biodegradability higher than 90% after150 days.

1. Composition comprising: (A) at least one biodegradablealiphatic-aromatic copolyester obtainable starting from mixturescomprising at least one diol, at least one polyfunctional aromatic acidand at least two aliphatic dicarboxylic acids, characterized in that thecontent of said aromatic acids is comprised between 48 and 70% by moleswith respect to the total molar content of dicarboxylic acids and thealiphatic dicarboxylic acids comprise: i from 51 to 95% by moles of atleast one diacid C₄-C₆; ii from 5 to 49% by moles, preferably from 30 to49% of at least one long chain diacid having more than 6 carbon atoms inthe main chain (B) at least one polymer of natural origin; wherein theconcentration of (A), with respect to (A+B), is >40% in weight, saidcomposition having a Melt Flow Index (MFI) of 1.5-10 g/10 min. 2.Composition according to claim 1, wherein said at least one long chaindiacid of said at least one biodegradable aliphatic aromatic copolyesteris selected from the group consisting of aliphatic dicarboxylic acidswith number of C atoms in the main chain comprised between 7 and 22,esters and mixtures thereof.
 3. Composition according to claim 1,wherein said aromatic acids are dicarboxylic aromatic compounds of thephthalic acid type and dicarboxylic heterocyclic aromatic compounds ofrenewable origin, mixtures and esters thereof.
 4. Composition accordingto claim 1, wherein said at least one polymer of natural origin isselected from starch, cellulose, chitin, chitosan, alginates, proteinssuch as gluten, zein, casein, collagen, gelatin, natural rubbers, rosinacid and its derivatives, lignins and their derivatives.
 5. Compositionaccording to claim 4, wherein said starch is in destructurized orgelatinized form or in filler form.
 6. Composition according to claim 4,wherein said starch represents an homogeneously dispersed phase ofparticles with mean dimensions of less than 1 μm.
 7. Compositionaccording to claim 1, biodegradable in accordance with the EN 13432standard.
 8. Composition according to claim 1, wherein said compositionis blended with one or more polymers.
 9. Blend comprising thecomposition according to claim 8, wherein said one or more polymers areselected from biodegradable polyesters of the diacid-diol, hydroxyacidor polyester-ether type.
 10. Blend according to claim 9, wherein saidpolyesters of the diacid-diol type are aliphatic or aliphatic-aromatic.11. Blend according to claim 10, wherein the content of saidbiodegradable polyesters from diacid-diol varies within the rangebetween 1 and 99% by weight.
 12. Blend according to claim 9, whereinsaid polyesters of the hydroxyacid type are selected from poly-L-lacticacid, poly-D-lactic acid and poly-D-L-lactic acid stereocomplex,poly-ε-caprolactone, polyhydroxybutyrate, polyhydroxybutyrate valerate,polyhydroxybutyrate propanoate, polyhydroxybutyrate hexanoate,polyhydroxybutyrate decanoate, polyhydroxybutyrate dodecanoate,polyhydroxybutyrate hexadecanoate, polyhydroxybutyrate octadecanoate andpoly-3-hydroxybutyrate-4-hydroxybutyrate.
 13. Blend according to claim12, wherein the content of said biodegradable polyesters from hydroxyacid varies within the range between 1 and 99% by weight.
 14. Blendcomprising the composition according to claim 8, wherein said one ormore polymers are selected from polyolefins, non-biodegradablepolyesters, polyester- and polyether-urethanes, polyurethanes,polyamides, polyamino acids, polyethers, polyureas, polycarbonates andmixtures thereof.
 15. Blend according to claim 14, wherein the contentof said polyolefins, non-biodegradable polyesters, polyester- andpolyether-urethanes, polyurethanes, polyamides, polyamino acids,polyethers, polyureas, polycarbonates and mixtures thereof varies withinthe range from 0.5 to 99% by weight.
 16. Blend comprising thecomposition according to claim 8, wherein said one or more polymers areselected from rigid polymers with a modulus greater than 1,500 MPa. 17.Blend according to claim 16, wherein the content of said rigid polymersvaries within the range from 5 to 30% by weight.
 18. Blend according toclaim 17, wherein said rigid polymers form an homogeneously dispersedphase of particles with mean dimensions of less than 2 μm.
 19. Blendaccording to claim 18, wherein said rigid polymers are polymers orcopolymers of polylactic acid containing at least 75% of L-lactic orD-lactic acid or combinations thereof.
 20. Blend comprising thecomposition according to claim 8, obtained by a reactive extrusionprocess with compounds carrying groups which can react with OH and/orCOOH groups, or with unsaturated bonds.
 21. Films, injection moldingarticles, extrusion coatings, fibers, foams, thermoformed articlescomprising the composition according to claim 8 or a blend thereofwherein said one or more polymers are selected from biodegradablepolyesters of the diacid-diol, hydroxyacid or polyester-ether type. 22.Use of composition according to claim 8 or a blend thereof wherein saidone or more polymers are selected from biodegradable polyesters of thediacid-diol, hydroxyacid or polyester-ether type for the production of:mono- and bi-oriented films, and films multilayered with other polymericmaterials; films for use in the agricultural sector; cling films for usewith foodstuffs, for bales in agriculture, and for wrapping waste; seeddressings; glues; bags and bin liners for the organic waste collection;thermoformed foodstuff packaging, both mono- and multi-layered; coatingsobtained using the extrusion coating method; multilayer laminates withlayers of paper, plastic, aluminum, or metalized films; expanded orexpandable beads for the production of pieces obtained by sintering;expanded and semi-expanded products, including foam blocks formed usingpre-expanded particles; foam sheets, thermoformed foam sheets, andcontainers obtained from them for use in foodstuff packaging; fruit andvegetable containers; composites with gelatinized, destructurized and/orcomplexed starch, natural starch, flours or vegetable or inorganicnatural fillers; fibers, microfibers, composite microfibers wherein thecore is constituted by rigid polymers such as PLA, PET, PTT, blendedcomposite fibers, fibers with different sections, from circular tomultilobed, staple fibers, woven and nonwoven fabrics or spunbonded orthermobonded for use in sanitary and hygiene products, and in theagricultural and clothing sectors.